user-accounts: Generate a default avatar for new users

When a user is created, we generate an avatar with their initials.

See https://gitlab.gnome.org/GNOME/Initiatives/issues/6

panels/user-accounts/user-utils.h

@@ -21,6 +21,7 @@
 #pragma once
 
 #include <gtk/gtk.h>
+#include <act/act.h>
 
 G_BEGIN_DECLS
 
@@ -44,4 +45,8 @@ gboolean is_valid_username                (const gchar *name,
                                            gchar      **tip);
 GdkPixbuf *round_image                    (GdkPixbuf  *pixbuf,
                                            gint        icon_size);
+void       generate_user_avatar           (ActUser *user);
+void       set_user_icon_data             (ActUser     *user,
+                                           GdkPixbuf   *pixbuf);
+
 G_END_DECLS